Method of continuously heat-treating products in sealed containers, and apparatus for performing the same

ABSTRACT

Method and apparatus for thermal treatment of products contained in sealed containers, in which the containers are conveyed along a path of travel comprising in succession at least one inlet hydrostatic pressure column, at least one treatment chamber under pressure and at least one outlet hydrostatic pressure column, the containers traveling in said chamber in contact with a liquid contained in said chamber and maintained to a predetermined treatment temperature, the liquid and its vapor in said chamber being subjected to an overpressure with a gaseous fluid, the pressure of which is constantly maintained at a value greater than the vapor pressure of said liquid at said treatment temperature, said overpressure being balanced by said hydrostatic columns.

Unlted States Patent 11113,619,126

|72] Inventor PlerreCarvallO 2,660,512 ll/l953 Webster 21/56 ztavlllaDuponcaris,ltSemeSeinev 3,340,791 9/1967 Mencaccieta|.... 99/362 France 2,733,651 2/1956 srimpsonetal. 99/362 1211 AppLNo. 398,240 2,968,232 1/1961 Carvallo 99/362UX [221 Filed SpL9229l7964 [451 Paemed N0 l 1278910 11/1961 F rance 21/80 Priority gfgnwslbee.1o,1%3,Ap1-.14,|%4 '90.132 11H90., Germany i 974,659 11/1964 GreatBritain [3H 949l46957250'970'824 731,550 6/1955 oreatritain [54] METHOD OF CONTINUOUSLY HEAT-TREATING PRODUCTS IN SEALED CONTAINERS, AND APPARATUS FOR PERFORMING THE SAME l1 Claims, 19 Drawing Figs.

Primary Examiner-Morris O. Wolk Amman! Examiner-Barry S. Richman Anumey-Waters, Roditi, Schwanz & Nissen ABSTRACT: Method and apparatus for thermal treatment of products contained in sealed containers, in which the containers are conveyed along a path of travel comprising in succession at least one inlet hydrostatic pressure column, at least one treatment chamber under pressure and at least one outlet hydrostatic pressure column, the containers traveling in said chamber in contact with a liquid contained in said chamber and maintained to a predetermined treatment temperature, the liquid and its vapor in said chamber being subjected to an overpressure with a gaseous fluid, the pressure of which is constantly maintained at a value greater than the vapor pressure of said liquid at said treatment temperature, said overpressure being balanced by said hydrostatic columns.

PAENTEDunv 9 lan SHEET B UF 6 METHOD OF CONTINUOUSLY HEAT-TREATING PRODUCTS IN SEALED CONTAINERS, AND APPARATUS FOR PERFORMING THE SAME This invention relates to a method of continuously heattreating products in sealed containers and to apparatus for performing the same, examples of such products being canned food, beverages, pharmaceutical products and the like, the invention being more particularly concerned with a continuous sterilization and cooling process carried out under hydrostatic pressure.

In apparatus resorted to heretofore, sterilization usually takes place in a chamber containing steam maintained under pressure: a column of water of given height maintains this pressure and serves as a passageway for introducing and withdrawing the products.

The temperature prevailing in such a chamber depends on the pressure. Now when products in sealed containers are heated, the pressure inside the containers becomes greater than the external pressure, so that it is necessary to design and use containers and seals capable of withstanding the stresses developed thus by the internal overpressure.

The present invention has for its object to permit, by working with an external hydrostatic overpressure, the use of containers or container sealing means which are incapable of withstanding an internal overpressure or which are not strong enough to be processed by normal methods.

It is accordingly one object of the invention to provide a method of continuously heat-treating products in sealed containers, consisting in treating said products in at least one chamber containing a liquid raised to the required temperature and which is kept at an overpressure by means of a gaseous fluid whose pressure is in turn kept constant by at least one column containing a liquid, through which column said products enter the processing chamber and emerge therefrom in continuous fashion.

In an alternative way of performing the method hereinbefore described, and in order to considerably improve the efficiency of the heat exchange process with the treated products, the liquid which is raised to the required temperature under gaseous overpressure may be caused to act upon the containers not only by immersion, but also by streaming, spraying, misting and atomization. This avoids the use of too large a volume of liquid and the expenditure of setting under temperature, thus enabling operating time to be cut down. Moreover, the heat transfer is improved through speeding up of the circulation rate over the container walls; also, this avoids subjecting the containers to pressures that vary with immersion depth.

Another advantage of this alternative form is the readiness with which the sterilization process can be halted and resumed in cases where the conveyor is stopped deliberately or inadvertently, since all that is necessary is to halt the spraying or streaming action at the same time.

Such a method additionally permits easy conversion of existing sterilization apparatus for the purpose of adapting the spraying components to them and thereby conferring upon them the advantages cited precedingly.

Still another advantage stemming from the spraying type of treatment is that it enables the processed containers to be agitated as a result of the high-pressure spray jets impinging upon them.

In yet another alternative mode of performing the subject method of this invention, the action exerted on the containers is made more thorough by so directing the liquid circulation streams that the contact taking place between these streams and the containers to be processed be extended and improved.

In accordance with the present invention, in cases where a spraying system is utilized, the liquid is accordingly sprayed in lateral and preferably staggered jets whereby to cover the entire area presented by the containers passing through the treatment chamber.

The spraying may be performed mechanically under the effect of the pressure imparted to the liquid, or else indirectly through entrainment by steam or compressed air.

ln cases where the path followed by the sealed containers to be processed includes two parallel passageways crossed in opposite directions, for instance, the jets may be given complementary conical shapes between said passageways in order that they should reach the entire area of the containers or that of the means used to convey them.

In accordance with the present invention, where misting is used it is preferable to impart to the cloud bathing said containers a very active circulatory motion within the treatment chamber in order to improve heat transfers and make the ambient atmosphere homogeneous throughout the volume of the treatment chamber.

Another object of the invention is to provide apparatus for performing this method, in which apparatus an endless conveyor successively traverses downwardly a liquid pressurecolumn, a first upwardly directed retrogression along the path, a treatment chamber containing a liquid at a required temperature subjected to the pressure of a gaseous fluid, a chamber in which said conveyor follows a path which conducts it to a second upwardly directed retrogression for exit into a liquid pressure-column and in which are combined introducing and pressure-maintaining means for introducing and maintaining said gas in said chamber and temperaturemaintaining means for maintaining said temperature of said treatment liquid at a value such that the vapor pressure of said liquid in said gas be less than said pressure.

ln specific instances where a spraying of the liquid is used in performing the method, it is highly advantageous for the container-transporting receptacles, consisting of open-ended cylindrical tubes, long pouches open in front, or angle irons, to be perforated over their entire length or over all their faces in order to permit a vertical streaming effect successively through these conveyors.

The description which follows with reference to the accompanying nonlimitative exemplary drawings will give a clear understanding of how the invention can be carried into practice and will disclose other advantageous features thereof which naturally fall within the scope of the invention.

In the drawings,

FIG. l shows in schematic section a first form of embodiment of a sterilizing apparatus according to the invention;

FIGS. 2 and 3 are alternative forms of embodiment thereof;

FIG. 4 shows, on an enlarged scale, a further alternative embodiment in which the treatment chamber is provided with substantially and essentially horizontal conveying paths;

FIG. S shows another constructional form similar to that of FIG. 4 but in which the conveyor loading and unloading station is located at a level below that of the entrance and exit column heads, and in which the entrances and exits of the sterilization chamber are transferred to the same side of the apparatus;

FIG. 6 shows an alternative embodiment in which the entrance and exit columns are fractionated;

FIG. 7 shows a first driving arrangement utilizing chains and sprocket wheels adjustable on their hubs;

FIG. 8 is an alternative arrangement to that of FIG. 7, for use with a transmission system utilizing gearwheels with verniers and an adjustmentjack;

FIG. 9 shows in schematic section an apparatus according to a second form of embodiment of the invention;

FIGS. 10 and 1I are alternative embodiments thereof;

FIGS. 12 through 14 illustrate other alternative embodiments;

FIG. I5 is yet another alternative embodiment;

FIG. 16 shows in cross section a processing apparatus in which the jets are staggered;

FIG. 17 is a section taken through the line XVII-XVII of FIG. 16;

FIG. 18 shows in similar fashion to FIG, I6 a section taken through a misting apparatus utilizing a forced circulation of the mist; and

FIG. 19 is a section taken through the line XIX-XIX of FIG. 18.

The sterilization apparatus shown in FIG. l comprises an entrance water column 1 whose height corresponds to the required pressure and at the base of which the conveyor chains 2 pass over idler wheels 3 which turn the chains back upwardly along their path. The base of the column l communicates with an entrance 4 whereat the liquid of the column l is maintained at a lower level within a space 5 in which prevails an air pressure maintaining the column liquid at a level 6 close to the head of the column. The space S contains a further direction-reversing system of idler wheels 7 which turn the chains downwardly into a liquid contained in` a sterilization chamber 8 arranged within the apparatus itself, between rising partitioning walls 9. Above the bottom of this chamber is a further direction-reversing system 10 which causes the conveyor to rise once more out of the liquid in the chamber 8. Above the second wall 9 of this chamber, in the space S, is another direction-reversing system ll which causes the conveyor to descend and to pass through a liquid at the bottom of an exit column l2, while a further direction-reversing system 13 leads the conveyor beneath the internal wall of said column. Above the two columns are positioned idlers 14, 15, whereby the conveyor is looped back onto itself. Along the loop-closing path is located a station I6 for loading and unloading the conveyor chains 2.

Referring next to FIG. 2, the bottom I7 of the entrance column la constitutes the bottom of a space 18 which is surmounted by the bottom 19 of a raised sterilization chamber 8a, and one of the walls 9a of said chamber 8a separates the latter from a space 20 which is closed by a bottom surface 21 substantially level with the bottom 19. Into this space 20 opens the foot of an exit column 12a which is separated from the entrance column la only by a partition 22.

yln such an arrangement the path followed by the conveyor includes a descent into the column la, twin idler systems 3a, 3b in the space 18 followed by a horizontal path therebetween, an upward path past the idler wheels 3b and along the length of the wall 9b of chamber 8a, a direction-reversing wheel system 7a above the head of the partition 9b, a descending path into the sterilization chamber 8a down to a bottom direction-reversing system 10a, an ascending path up to an exit direction-reversing system 11a, a descending path down to a direction-reversing system 13a at the foot of the column 12a, an ascending path into said column 12a, followed by a passage over a direction-reversing system 14a located above the partition 22 separating the columns 1a and 12a. A loading and unloading station 16a is positioned above the heads ofthe columns beneath the direction-reversing system 14a. For greater simplicity, all direction-reversing or changing systems will hereinafter be referred to as idlers The space surmounting the sterilization chamber 8a and the feet of the columns is closed, said space containing the idlers 7a and 11a and containing air under pressure. This air acts on the water level at the foot of the columns whereby to maintain the upper level thereof at the required height.

In this form of embodiment the entrance and exit columns are adjacent and located on the same side of the apparatus.

In the constructional form schematically illustrated in FIG. 3, the apparatus is identical but the conveyor includes an external lower offset loop enabling the loading and unloading station 16h to be moved level with the bottom of the sterilization apparatus by means of idlers 22, 23 positioned at the heads of the columns 1b and 12b respectively. Beyond the idler 23 extends a horizontal path up to an idler 24, whence the path extends vertically down to an idler 25. Ahead of the entrance idler 22 is a likewise vertical path extending from a foot idler 26 level with the idler 25. These idlers 2.65 and 26 flank a raised idler 27 beneath which is located the loading and unloading station lb.

The various dispositions hereinbefore described are devised in such manner that the paths followed by the conveyor through the sterilization chambers are vertical. FIG. 4, however, shows an arrangement in which these paths are essentially horizontal. Accordingly, the conveyor 2c descending through an entrance column 1c passes beneath an idler 3c before emerging into the offset part of the foot of this column. lt then passes over an idler 7c above one of the partitions 9c bounding the sterilization chamber 8c containing water enclosed in a sealed space 5c and subjected to the pressurized air filling this space. Consecutive stepped idlers 10c in the chamber 8c enable horizontal conveyor runs 28 to be formed, while the last bottom idler 29 located in the corner diagonally opposite the corner nearest the idler 7c enables the conveyor to be led out vertically from the liquid in the chamber and to pass over an exit idler llc.

The conveyor then follows a descending path into a laterally located column 30, and then passes through a tunnel 31 after running over an idler 13b, said tunnel being arranged beneath the chamber 8c. The conveyor then passes over an idler 13C at the foot of the exit column 12C, which column is located adjacent the entrance column lc. An idler 14C at the head of the columns enables the conveyor to be looped back onto itself. and beneath this idler is disposed a loading and unloading station 16C.

Reference is now had to FIG. 5 for the illustration of an apparatus of the same kind arranged in similar fashion to that of FIG. 4, except for the provision of entrances and exits located on the same side of the sterilization chamber and also of a baffle in the tunnel beneath said chamber. A further exception is the transfer of the loading and unloading station to a low level, by an arrangement similar to that of FIG. 3.

Referring still to F IG, 5 for a more detailed description, this particular constructional form comprises an entrance column ld below which an idler 3d guides the conveyor chains upwardly over two spaced idlers 7d, 7e placed above and on either side of the wall 9d bounding the sterilization chamber 8d, Above this wall is likewise provided a single lower idler 11d which redirects the emerging conveyor downwardly along the wall 9d. At the foot of this downward path, in the midst of the liquid at the foot of the entrance column ld and in the offset part thereof, is located an entrance idler 3f into a tunnel 31d having therein a baffle 32 facing which is located a bottom idler 3e which redirects the conveyor towards an idler 13d paced at the bottom of the exit column 12d. Above this column 12d is an idler 22d and above the associated entrance column ld is an idler 23d preceded by an idler 24d. The loop is closed between idler 24d and idler 22d via two idlers 25d and 26d, between which is positioned a raised idler 27d beneath which is located a loading and unloading station 16d, the latter being thus relocated near the bottom of the apparatus, approximately level with the supporting floor.

The pressurized air for pressurizing the water in the sterilization chamber 8d is conveyed, through a pipe 33 equipped with a valve, to the top of the chamber which closes the foot of the entrance column 1d, the water level at said foot being comprised between said partition 9d in the lower part of the apparatus and a point near the lower edge 34 of one of the dependent walls of the column ld. This edge automatically regulates the maximum air overpressure, since excess air finds its way beneath the edge 34 and out through the column ld. This water level also constitutes the level which ensures filling of the subjacent tunnel 31d and additionally forms, by way of said tunnel, the level at the foot of the exit column 12d.

Considering now the methodical circulation of the water, a cold water inlet 3S regulated by a thermostat valve and possibly also by a constant-level float-valve is provided at the head of the exit column 12d, as may likewise be the case for all the other constructional forms described precedingly.

By a counterstreaming process, this cold water methodically cools the emerging products travelling in the opposite direction, i.e. ascending the exit column 12d. The gradually heated water passes through the baffle-tunnel 31d and is hot when it reaches the foot of the entrance column ld. While still being counterstreamed, this hot water is cooled in column ld and at the same time preheats the products descending therethrough on the conveyor 2d.

The water cooled thus spills from the column 1d by way of an upper spillway 36 whose level regulates the required water pressure.

Because the intake of cold water into the exit column is adjusted by a temperature-sensitive device such as a suitably located adjustable thermostat, the ultimate cooling temperature on emerging from the exit column 12d will invariable be below a specified temperature.

In order to save water and heat and maintain the upper levels in the pressure columns notwithstanding the wide variations often occuring in the degree to which, for various external reasons, the conveyor is loaded with objects to be processed, which cause the loading and unloading station to be supplied nonuniformly, compensation is made either for the often massive expulsions of water which may occur following the transition from operation with a lightly loaded conveyor 2d to operation under full load, or, conversely, for the often massive intakes of cold water which could occur through the inlet 35, by associating with the spillway 36 a buffer tank 37 which is itself provided with an overflow 38.

With this tank is further associated an offtake pump 39 which draws from the bottom of the tank and delivers through a nozzle 40 located above the column 1d. The pump 39 thus compensates for drops in the level of the columns when, for instance, the conveyor is loaded to less than its maximum capacity, whereby the level corresponding to the correct overpressures in the apparatus is restored, Moreover, the residual heat of this returning water is not lost for warming up the products entering the apparatus.

Considering next the pressures, the water temperature in the chamber 8d, as in the previous constructional forms described, is maintained, by regulated steam-type heating means (not shown), at a constant suitable value such that the steam pressure at that temperature be less than the counterpressure exerted by the air and which is given by the water column existing between the edge 34 and the spillway 36, which two elements, in conjunction with the intake to the pump 39, contribute toward maintaining this water column height at a constant value.

Inside the tunnel 31d, the baffle 32 helps to correctly grade the cooling temperatures of the products issuing from the chamber 8d, by making use of the tendency resulting from variations in the density of the circulating water. In the columns, on the contrary, the density effect opposes such a grading, and this is offset by making the columns as narrow as possible in order that the products and the supporting receptacles therefor carried along by the conveyor, in conjunction with the water circulation rate, produce a water entrainment effect greater than that resulting from density variations.

Since the overpressure to be obtained on the water in the sterilization chamber may have to be great, the height of the entrance and exit columns for the products to be processed could become prohibitive. This is overcome by fractionating the height of the columns and by inserting between the fractionated sections compressed-air relay-columns, as shown in FIG. 6.

In the alternative constructional form shown in this figure, the sterilization chamber exit tunnel is laid out differently from that of FIG. 5. In FIG. 6, the latter portion of the tunnel passes above the sterilization chamber. This in turn means that such a tunnel must be made relatively narrow since the beneficial effects ofthe water density variations no longer exist.

Another essential difference between the embodiments of FIGS. 5 and 6 is that the entrance column comprises a section le whose bottom communicates with a relay-forming air column 1f the top of which in turn communicates with the second column section lg likewise filled with water.

Similarly, the exit column comprises a first section 12e communicating through its base with an air relay column 12f the top of which in turn communicates with the second section 12g of the exit column. This section 12g has its bottom connected to the upper run of the exit tunnel 31g, and this tunnel communicates, via an extension beneath the sterilization chamber 8e, with the base of the column lg.

The compressed air needed to obtain the required overpressure may be introduced through a pipe 41, preferably very close to the water level within the space bounded by the lower edge 34e of one of the internal walls of column lg and the top of the wall 9e of the chamber 8e. This pressurized air can if necessary find its way beneath the edge 34e into the internal space corresponding to the relay column 1f. A balancing pipe 42 is connected across the heads of relay columns l f and l2f.

With such an arrangement the air overpressure is maintained automatically constant and equal to the sum of the pressures exerted by the water columns on the liquid in the chamber 8e, while the two different pressure values required in the relay columns are also maintained. The excess compressed air passes round the base of the columns le or 12e and escapes from the heads of these columns.

Considering next the water circulation, cold water can be admitted through a pipe 43 in quantities regulated by a floatvalve 44 which ensures a constant level in the head of the second exit column section 12e. At the foot of this section 12e is provided a pump 45 whose output is regulated by a thermostat-controlled valve 46 which feeds a pipe 47 for introducing the required quantity of water in the head of the exit column section 12g, such thermostatic control enabling the desired temperature values and gradings in the column 12g and the tunnel 31g to be obtained. The water is thus counterstreamed in the fractional sections of the exit column and also through the tunnel 31g. This water also counterstream-feeds the column 1g and, by overflowing'from the head of column lg into column lf, additionally supplies the column le, from which it can overflow into a compensating tank 37e of the same kind as that described with reference to FIG. 5. A pump 39e at the foot of the tank restores the level in the head of column le via a delivery pipe 40e. A second pump-equipped tank could be provided to ensure a similar volumetric comv pensation into the top of the column lg.

Obviously, the form of embodiment of FIG. 6 comprises the necessary idlers at each change of conveyor direction, in similar fashion to the constructional form described with reference to FIG. 5, with additional idlers located at the extremities of the fractional sections of the water and air relay columns.

Apparatus devised as described hereinabove require a total conveyor length which can sometimes be considerable. For example, an apparatus operating at 120 C. in the sterilization chamber with an overpressure of about kPa will require entrance and exit columns containing water to a height of approximately 2() meters unless they are subdivided, though it will be appreciated that any such subdivision will lengthen rather than shorten the total conveyor path. For a sterilization time of about 20 minutes and an hourly output of 300 containers, each containing about grams of a substance to be sterilized, the total conveyor length required under such conditions would be about meters.

With such a great length and correspondingly large number of idlers, any attempt to drive the conveyor from a single point only would involve exerting forces which neither the chains nor the idler bearings could be expected to withstand if the cost of building such an apparatus is to be kept within reasonable limits.

It is therefore preferably to drive the conveyor simultaneously from several different points in order to reduce the stresses set up.

As shown in FIGS. 5,7 and 8, the driving force which is applied, say, to the shaft of the idler 27d acting as a principal drive unit synchronized with the mechanisms of the loading and unloading station 16d, is transmitted externally of the apparatus, through a sprocket wheel 48 and a chain 49 to a sprocket wheel 50 rigid with the shaft of the idler 11d at the exit of chamber 8d, thereby forming a transmission interconnecting two shafts rotating in the same direction.

lf, however, it be desired to provide a mutual drive for two adjacent idler shafts rotating in opposite directions, as is the case for instance with the shafts of the exit and entrance column head idlers 22d and 24d respectively, the said shafts may be rigidly connected to externally meshing equal gearwheels 50 and 51. One of these shafts may act as a driving member driven by the conveyor chains themselves, in cases where the idlers are toothed sprockets meshing positively with the chains. The shaft of the second gearwheel is made rigid with similar sprockets whereby to positively drive the conveyor chains running over them. In the example of lFIG. 5, the shafts of idlers 22d and 24d are independent of the principal drive shaft of idler 27d, but it will be manifest that a transmission other than that supplied by the conveyor chains themselves could be used.

It will be of advantage to provide external transmission between a main shaft and second drives, by distributing these secondary drives uniformly over the length of the conveyor, while making due allowance for the resistances encountered (which are greater along horizontal paths) and for the number of idlers comprised between the drive members.

Driving an endless conveyor at several points requires certain precautions in order that the external drives and those transmitted through the internal chains should not counteract one another as the result, firstly, of possible irregularities in the various chains sections and, secondly, of expansion effects due to passage through parts of the apparatus raised to greatly differing temperatures. It is therefor important to provide suitable clearances and to determine precise settings on the idlers which separate the various sections of the path and which act as drive points.

In order to facilitate such adjustment yet avoid having to remove the chains from the sprockets, the external drive wheels are mounted in angularly adjustable manner on the corresponding shafts. By way of example, the sprockets 48 and 50 interconnected by an external chain 49 have hubs 52 and 53 which can be mounted adjoining drive flanges keyed or welded to the shafts. The hubs and the flanges have holes formed, therein, through which pins or studs parallel to the shafts can be threaded. Such a flange may comprise, for instance, a set of 2O regularly spaced holes and the hub 53 a set of likewise regularly spaced holes S4, the two sets of holes being located on circles of equal radius. With such an arrangement, in which four of the holes on the hub 53 will always register with four of the holes on the flange, the sprocket 50 can be made rigid with its shaft by means of four bolts or pins, the angle between two consecutive registerings being only oneeightieth of a revolution. A quadruple Vernier adjustment is extremely precise as regards the respective positions of the internal conveyor chains and the external drive chains, while at the same time permitting secure attachment by four bolts. Different effects could be obtained by providing single, double, triple, or more verniers.

As FIG. 8 clearly shows, there is interposed between the vernier hub 55 of gearwheel 5l andthe latter (which is loosely mounted on its hub), an abutment 56 rigid with the hub 55, a lobe 57 rigid with gearwheel 5l, and a bolt 58 which is screwed into lobe 57 and whose tip bears against the abutment 56. This makes it easy to obtain a displacement of the wheel relative to its shaft in spite of a possibly heavy load on the chains.

Moreover, such a long conveyor is necessarily subject to chain elongation. In order to correct this defect it is preferable to provide an elastically or nonelastically mounted tensioning idler at least at one point along the chain length. FIG. shows such a movably mounted idler 25d coupled to elastic tensioning means and additionally equipped with guiding rneans S9 of the conveyed objects, mounted telescopically relative to the fixed conveyor guides.

Manifestly, the various arrangements according to the invention hereinbefore described can be executed with any convenient conveyor system. In order to achieve the large throughputs required, the conveyors generally consist of two parallel endless chains interconnected by means of containercarrying receptacles bearing the products to be processed, or by means of sectional-iron supports forming socketlike receptacles into which the containers are inserted and from which they can be withdrawn subsequent to processing. Preferably, such a conveyor consists of two parallel endless chains equipped with thrust pegs which entrain, along a path coextensive with said chains, tubular receptacles into which said containers containing the products to be processed are inserted and subsequently extracted, said receptacles preferably not being attached to said chains.

These receptacles are preferably cylindrical which, by virtue of their being independent of the chains, enables them to revolve about themselves along the horizontal path sections, such as those provided in the sterilization chamber 8d, for instance. This autorotation of the receptacles produces a rotation of the containers themselves, which greatly improves the effectiveness of the heat treatment in a great many cases.

It goes without saying that should such container rotation prove a drawback with certain types of product, preference must be given to apparatus having exclusively vertical paths through the treatment chambers, or else steps must be taken to rigidly interconnect the conveyor and the receptacles in order to prevent any detrimental agitation.

Thus food and pharmaceutical or other products can be processed in this way, an example being childrens food, the processing being performed in glass, tin, aluminum or plastic containers of smaller thickness than usual and which comprise sealing means which, though entirely capable of withstanding an internal vacuum for sealing purposes, may or may not be capable of withstanding an internal compression.

The apparatus illustrated in FIG. 9 is of a disposition similar to that of the apparatus of FIG. l, like parts being designated by like reference numerals. In the apparatus of FIG. 9, however, the liquid level in the column 8 formed inside the treatment space is located right at the bottom of the column, from which a pump 60 draws said liquid (water, for example) and conveys it through a riser 61 into gutters 62 located at the top of the riser, said gutters being provided with spillways which spread the streaming water over the entire width of said riser. The spillways may be supplemented if necessary by spraying effected by means of nozzles 63 suitably spaced along the riser 61. Depending on the fineness of the droplets, these nozzles may provide ordinary spraying, misting, or atomization, and any one of these results can be obtained by the use of means well known per se.

The gas under pressure air, for example is admitted through an inlet 33 located in the roof of the chamber 8 and its ancillaries. This pressurized gas maintains the chamber 8 at a pressure equal to the height of the column of liquid located above the edge 34 of the wall bounding the space 4 adjacent the chamber 8, and any excess compressed air can pass beneath this edge 34 and out through the column l into the surrounding atmosphere after passing through the upper level 6 of the water contained in said column. Such a disposition consequently provides autoregulation of the pressure.

The water temperature at the foot of column 8 is maintained by heat exchanger means (not shown) for which the heat supply is governed by a thermostat-regulator of any convenient type (not shown). This temperature is so regulated that the vapor of the liquid, at the temperature in question, be at a pressure below the air pressure maintained in the chamber.

It will be seen that with such an arrangement the height of the column 8 can be as large as desired, the water level at the bottom being relatively low, and that the walls 9 can be as high as necessary. The time taken by the conveyor 2 to pass through the chamber 8 is therefore longer. This means that the sterilization treatment is made more thorough without the need to reduce the conveyor speed. The thermal efficiency is augmented as regards the heat transfer between the water spray issuing from the nozzles 63 and the walls of the containers to be processed. These walls may be sprayed from beneath the spillways of the gutters 62, which gutters lie in the planes of the ascending and descending runs of the conveyor. These sprays impinging on the containers agitate the latter, which further assists the processing in certain cases. To that end the spray jets are made powerful enough to move the containers in their receptacles as they pass along, adequate clearance being naturally provided therein for the purpose.

The form of embodiment shown in FIG. 10 differs from that of FIG. 9 chiefly by the suppression of the upwardly located idlers 7 and 11 and by the consequent reduction in volume of such intermediate spaces as the space 4. On the other hand, the pressurized chamber 8f used for the processing is shaped as a bell uptumed above an open vat 9f.

This being so, the edge 34j" of the chamber 8f will enable the compressed air to pass into spaces f and 5g whereat meet the feet of the entrance and exit columns I and l2 which are positioned on either side of the walls 9g and 9h of the vat 9f, with downwardly dipping edges 34g and 34h respectively. The compressed air is also able to pass beneath these edges 34g and 34h and out into the open atmosphere by passing up the columns 1 and 12. Thus, in this case also the pressure is regulated automatically in the chamber 8f.

The spaces Sfand 5g are interconnected via an air pipe 5h in order to ensure balanced pressures. In the spaces 5f and 5g are provided two downward-directing idlers 7f and 7g and, in the vat 9f, two upward-directing idlers 10f and 10g. A downward-directing idler 10h is provided at the top of the bell 8f. A riser 61a equipped with atomizers 63a is located within the bell 8f, above a pump 60a drawing water from the vat 9f.

The embodiment shown in FIG. 11 is a simplified constructional form which entirely eliminates the idlers 7, 7f and 7g of the previously described forms of embodiment.

Accordingly, the treatment chamber 8a is of bell shape and located above a space 9a which at the same time constitutes the feet of the entrance and exit columns 1 and l2. In this space is arranged at vat 9j of suitable heated water from which the pump 60i draws. This pump delivers the water into a riser 6l equipped with spray jets 63i. This riser divides into two upper branches 621' which are equipped with spray jets directed at the conveyor around the upper idler 10i positioned at the top of said space 8i.

In order to avoid overactive heat exchanges between the heated water in the vat 9j and the feet of the columns, the water level is established below the edges of said vat but above the edges 341' of the feet ofthe columns. To this end also, since the level at the foot of the columns must be kept above the edge 341', this level as well as the air pressure in the space 8i are regulated by a float mechanism 34j which operates a valve in the air inlet 33.

FIG. 12 shows a sterilizer of known type utilizing a conveyor 2 of the type in which tubular receptacles are entrained by two parallel chains through an entrance column l, a sterilization space 8k and an exit column 12.

On issuing from the column l2 the conveyor passes into a supercooling tank 12k having a wall 121 beneath which the conveyor passes. The water circuit is so devised that it be supplied through the column l2 and be discharged through the column 1 and that it circulates in the opposite direction to the conveyor. At the foot of the chamber 8k is placed a vat 9k beneath which is left a passageway 65 through which the water passes without too unfavorable a heat transfer taking place with the water used at the foot of the sterilization chamber. The arrangement used for heating the vat 9k is similar to that described preceding1y,i.e. by means of a heat exchanger and a thermostat, while the spraying system is identical to that shown in FIG. l1. Similarly, the water level is maintained by means ofa float 34k, positioned in similar fashion.

Reference is next had to FIG. 13 for the illustration of a sterilizer which utilizes joists 64 for conveying the containers, these joists being fixed to two parallel chains constituting the conveyor 2. Said joists jointly form sockets on either side of the plane containing the chains, and these sockets are caused to open through the chains alternately passing over staggered pulleys 16a, 16b around which the chains wrap to a sufficient extent to cause the two openings formed by each pair of cooperating joists to gape open consecutively. The configuration of the sterilizer is similar to that shown in FIG. l1, but in the example of FIG. 13 the spraying takes place in the treatment chamber 8l by means of triple spray pipes, due to the fact that the conveyor undergoes three direction reversals in said chamber and comprises four separate runs therein.

The final cooling can also be effected in a special column 65 adjacent the exit column 121, said column being located above a collector vat 66 positioned beneath the apparatus, and into said column 65 have port spray jets 67 which spray the corresponding conveyor run, these spray jets being supplied through a pipe 68 connected to the delivery end of a pump 69 drawing water from the vat 66.

The apparatus shown in FIG. 14 comprises a conveyor 2 with which cooperate container-conveying receptacles 70 of the type commonly used in bottle-washing machines and which are loaded and unloaded from the front at a station 16m.

The transformer which permits operation under pneumohydrostatic overpressure includes a recirculating and spraying pump 60m which draws the heated water from a vat 9m at the foot of the treatment chamber 8m and which delivers it into a spray pipe 63m, compressed air being admitted through an upper inlet 33 and the pressure being modulated by a float 64m, as described precedingly.

Next to the treatment chamber 8m is provided a similarly arranged cooling chamber 8n in conjunction with a pump 60n and spray pipes 63n. This chamber 8u communicates with the base of an exit column 12m to which adjoins a supercooling column 65m similar to that described precedingly and in which the spraying is effected through the agency of a pump 69m drawing water from a bottom vat 66m. Thus cooling is effected by spraying into the column 8n, at the same pressure as in the sterilization column 8m. The air pressure is balanced by a pipe 8t interconnecting these two columns.

The cooling water is circulated via a bypass 70a on the delivery side of the pump 69m, with subsequent discharge through a nozzle 73 above the column 12m. The flow is adjusted by a thermostat 72 which measures the water temperature at the foot of the column 12m and actuates the valve 7l at the entrance into the bypass 70a. The cooling water flows from the column 12m to the column 1m beneath the vat 9m.

Referring to FIG. l5, there is shown thereon an apparatus whose conveyor 2 uses tubular receptacles which are loaded and unloaded sideways at a station 16p, as described previously. This apparatus comprises two entrance and exit hydrostatic columns 1p and 12p, respectively, associated with preheating and precooling hydrostatic columns lq an I2q. Likewise provided is a treatment chamber 8p within which the conveyor sustains several reversals of direction. Also provided is a spray-type cooling chamber 8g. A spray-type supercooling column 65p is likewise provided as precedingly and. downstream of this column, the conveyor passes through a water-containing tunnel 74 which extends beneath the apparatus and which leads the conveyor to the station 16p.

A pump 69p recycles the water from the base of the tunnel 74 to the top of the column 12p by bypassing the spray circuit through the column 65p, as described precedingly, asimilar regulating system being provided by a valve 71p and a thermostat 72p. An additional pump 75 is provided to draw water from the foot of the column 12p and convey it to the top of the column 12q, in conjunction with a further pump 76 which draws the water overflowing from the column 1p into a vat 77 and conveys it to a nozzle 78 adjacent the nozzle 73p.

This ensures that the volumetric compensation and cooling water circulation functions are performed in the manner hereinbefore described.

As regards air pressure balancing, the distribution is ensured through a pipe 33p equipped with a valve 81 for intake into the chamber 8p. The pressures in the chambers 8p and 8q are balanced by a pipe 8r. Downstream of the valve 8l is provided a takeoff which comprises a valve 79 and from which air is conveyed into the space separating the foot of column Ip and the head ofcolumn lq. The pipe 80 balances the pressures between this space and the space separating the head of column 12q from the foot of column 12p.

The valve 81 is actuated by a float 64p located between heating vat 9p and the foot of the column lq. The valve 79 can be reduced to a simple calibrated jet, since any excess air in said column separating spaces can be discharged automatically through the feet of the end columns.

Obviously, pumps 60p and 60q which are counterparts of the pumps 60m and 601i, respectively, referred to precedingly, perform like functions.

In all the constructional forms described hereinabove with reference to FIG. 9 through 15, the disposition, orientation and delivery force of the spraying, misting or atomizing jets, with respect to the processed container, may be made such tat the latter receive, as they move along, agitating impulses which assist the processing and especially the heat transfer between the walls and the contents of the containers.

As FIG. 16 clearly shows, the treatment chamber 100 flanked by the overpressure columns 101 and 102` filled with the liquid forming a sealing and pressure-boosting means, provides a passage for the conveyor means 103 of the receptacles 104 bearing the sealed containers to be processed along a path which is ascending on one side and descending on the other.

At the foot of the chamber 100 is placed a liquid receptacle 105 whose base communicates through a pipe 106 with a pump 107. The delivery pipe 108 of this pump divides into two branches 109 and 110, which branches form staggered injector banks 1l l and 112 disposed along the opposite faces of the chamber 100 (see FIG. 17).

The injectors lll are designed in such manner that they emit conical jets whose apex angles are such that adjacent and opposed projection layers be substantially tangential, as shown in FIG. 17.

Moreover, these jets 111 and 112 lie in the saine vertical plane, which plane is the plane of symmetry with respect to the two runs of the conveyor 103 through the chamber 100.

In this chamber set under overpressure, therefore, the processing liquid expelled through the jets is susceptible of reaching almost the entire surface of the containers to be processed, as the result of multiple impacts which are favorable to a homogeneous treatment in conjunction with a highly active heat exchange coefficient.

Should only a single conveyor run be utilized, then instead of conical jets it would be preferable to use flat jets which, through staggered, will nevertheless cover virtually the entire surface ofthe containers to be processed or of the receptacles containing the same.

Manifestly, the spraying can be obtained mechanically or pneumatically, using steam or compressed air.

Reference to FIGS. 18 and 19 shows that when a treatment chamber 113 set under an overpressure is subjected to internal misting, it is preferable to associate with such a chamber a recirculating system by means of a fari 114 which draws the mist through a suction orifice 115 at the bottom of the chamber and impels it through a tube 1 16 and a reentry orifice 117 into the chamber l 13 near the top thereof, whereby to obtain an active circulation of the atmosphere and the mist container in the chamber, while at the same time rendering the ambient atmosphere in the internal space as homogeneous as possible, with the same advantages as hereinbefore cited.

This circulation can also be taken advantage of to bring in the steam required to create the mist, through a nozzle 118 which, in conjunction with the orifice 117, forms an ejectorlike device which assists the recycling process.

As may be seen from FIGS. 17 and 19, in which the conveyor receptacles illustrated are vertically moving tubular baskets perforated over their entire length and periphery, the treatment water streams from one to the other in succession and thus has maximum effectiveness.

It goes without saying that many modifications may be made to the specific embodiments described hereinabove without departing from the spirit and scope of the invention. By way of example, a single pressure column could be provided and could serve for both introducing and withdrawing the products to be processed. Similarly, fluids other than air and water could be used and, if a complex processing is involved, a

plurality of chambers could be provided and be traversed in succession. Lastly, as shown in FIG. 5, the water in the sterilization chamber could be agitated by means of a pump 60 which draws water ata low level and delivers it through a pipe 61 to a higher level.

What I claim is:

1. A heat treatment apparatus comprising means defining a sterilizing constant pressure chamber, means defining a U- shaped inlet hydrostatic housing with one end of said housing communicating with one end of said pressure chamber, means defining a U-shaped outlet hydrostatic housing with one end of said outlet housing communicating with the other end of said pressure chamber, means for directing a high-pressure heating medium into said pressure chamber, means for directing a liquid preheating medium into said U-shaped inlet housing, means for directing a liquid cooling medium into said U- shaped outlet housing, means defining two air chambers in open pipe connection with each other for applying a common overriding air pressure to the other ends of said housings, said air pressure being sufficient to maintain the level of liquid in each of said U-shaped housings at different elevations and to cooperate with the forces exerted by the so defined unbalanced portions of liquid to balance the pressure within said pressure chamber, and conveying means including carriers for supporting and moving articles into and through said U- shaped inlet housings, through said sterilizing pressure chamber, and through and out of said U-shaped outlet housing without disturbing the pressure balance within said housings.

2. A heat treatment apparatus comprising means defining a sterilizing constant pressure chamber, means defining a U- shaped inlet hydrostatic housing with one end of said housing communicating with one end of said pressure chamber, means deiining a U-shaped outlet hydrostatic housing with one end of said outlet housing communicating with the other end of said pressure chamber, means for directing a high-pressure heating medium into said pressure chamber, means for directing a liquid preheating medium into said U-shaped inlet housing, means for directing a liquid cooling medium into said U- shaped outlet housing, means defining two air chambers in open pipe connection with each other for applying a common overriding air pressure to ends of said housing, said air pressure being sufficient to maintain the level of liquid in each of said U-shaped housings and to cooperate with the forces exerted by the liquids to balance the pressure within said pressure chamber, and conveying means including carriers for supporting and moving articles into and through said U- shaped inlet housings, through said sterilizing pressure chamber, and through and out of said U-shaped outlet housing without disturbing the pressure balance within said housings.

3. Apparatus for continuous thermal treatment of products contained in said apparatus in sealed containers, comprising in combination an endless conveyor for transport of containers, a vessel having at least one inlet hydrostatic column, means defining at least one constant pressure treatment chamber communicating with said first column, and at least one outlet hydrostatic column communicating with said chamber, means for advancing said conveyor through said vessel along a path of travel successively passing through the inlet column, the treatment chamber and the outlet column, said treatment chamber including a major portion of substantially horizontal elongate form, a liquid filling said major portion of the treatment chamber, means for maintaining said liquid at a predetermined treatment temperature, means for introducing and for maintaining in said chamber a gaseous fluid having an overpressure, the value of which is greater than the vapor pressure ofv said liquid at said temperature, said overpressure being balanced by said columns, and idlers in said major portion of said treatment chamber for said conveyor arranged to cause the conveyor to travel in at least one substantially horizontal run through the liquid in said major portion of the chamber.

4. Apparatus for continuous thermal treatment of products container in said apparatus in sealed containers, comprising in combination an endless conveyor for transport of containers, a vessel having at least one inlet hydrostatic column, means defining at least one constant pressure treatment chamber communicating with said first column, and at least one outlet hydrostatic column communicating with said chamber, means for advancing said conveyor through said vessel along a path of travel successively passing through the inlet column, the treatment chamber and the outlet column, a liquid with its vapor in said chamber, means for maintaining said liquid at a predetermined treatment temperature, means for introducing and for maintaining in said chamber a gaseous fluid having an overpressure, the value of which is greater than the vapor pressure of said liquid at said temperature, said overpressure being balanced by said columns, and means in said treatment chamber for dividing the liquid and impinging the same under pressure at said treatment temperature against the containers along the length ofthe conveyor in said treatment chamber.

5. Apparatus as claimed in claim 4 wherein said means for dividing and impinging the liquid against the containers is located on both sides of the conveyor.

6. Apparatus as claimed in claim 4 wherein said means for dividing and impinging the liquid on both sides of the conveyor comprises a pump connected to a reservoir of said liquid, maintained in the chamber at said treatment temperature and overpressure, for circulating the latter liquid and effecting division and direct impingement thereof against the containers.

7. Apparatus as claimed in claim 4 comprising receptacles on said conveyor for receiving the containers, said receptacles being perforated over their entire surface to permit successive vertical streaming along their length.

8. A method of continuous thermal treatment of products contained in sealed containers, said method comprising the steps of conveying said containers along a path of travel comprising in succession at least one inlet hydrostatic pressure column, at least on treatment chamber under constant pressure and at least one outlet hydrostatic pressure column, forming said treatment chamber of substantially horizontal elongate shape, f'illing said chamber with a liquid, maintaining the liquid at a predetermined treatment temperature, subjecting said liquid in said chamber to an overpressure with a gaseous fluid, the pressure of which is constantly maintained to a value greater that the saturated vapor pressure of said liquid at said treatment temperature, said overpressure being balanced by said hydrostatic columns, and passing the conveyor along at least one immersed horizontal run in the liquid in said chamber.

9. A method of continuous thermal treatment of products contained in sealed containers, said method comprising the steps of conveying said containers along a path of travel comprising in succession at least one inlet hydrostatic pressure column, at least one treatment chamber under constant pressure and at least one outlet hydrostatic pressure column, subjecting said containers traveling in said chamber to the action of a liquid contained in said chamber and maintained at a predetermined treatment temperature, subjecting said liquid and its vapor in said chamber to an overpressure with a gaseous fluid, the pressure of which is constantly maintained to a value greater than the saturated vapor pressure of said liquid at said treatment temperature, said overpressure being balanced by said hydrostatic columns, said containers being subjected to the action of said liquid by dividing the liquid and impinging the same against the containers at said treatment temperature and pressure along the length of travel in the treatment chambers.

10. A method as claimed in claim 9 wherein liquid is maintained in the treatment chamber in a reservoir at the bottom thereof, and the liquid which impinges on the containers is recirculated from said reservoir.

l1. Apparatus for continuous thermal treatment of products contained in sealed containers, comprising an endless conveyor for transport of containers, a vessel having at least one inlet hydrostatic column, I at lest one vertical treatment chamber communicating with said first column, and at least one outlet hydrostatic column communicating with said chamber, means for advancing said conveyor through said vessel along a path of travel successively passing through the inlet column, the treatment chamber and the outlet column, a treatment liquid at the bottom of said vertical chamber, means for maintaining said liquid at a predetermined treatment ternperature, means for introducing a gaseous fluid into said chamber and for maintaining at a constant level the said liquid and foi? maintaining inside the treatment chamber a constant overpressure the value of which is greater than the vapor pressure of said liquid at said treatment temperature, said overpressure being balanced by said hydrostatic columns, and a circulating pump for pumping the treatment liquid at the bottom of the treatment chamber and spreading it in divided form at the top of the said treatment chamber.

lk Ik 

2. A heat treatment apparatus comprising means defining a sterilizing constant pressure chamber, means defining a U-shaped inlet hydrostatic housing with one end of said housing communicating with one end of said pressure chamber, means defining a U-shaped outlet hydrostatic housing with one end of said outlet housing communicating with the other end of said pressure chamber, means for directing a high-pressure heating medium into said pressure chamber, means for directing a liquid preheating medium into said U-shaped inlet housing, means for directing a liquid cooling medium into said U-shaped outlet housing, means defining two air chambers in open pipe connection with each other for applying a common overriding air pressure to ends of said housing, said air pressure being sufficient to maintain the level of liquid in each of said U-shaped housings and tO cooperate with the forces exerted by the liquids to balance the pressure within said pressure chamber, and conveying means including carriers for supporting and moving articles into and through said U-shaped inlet housings, through said sterilizing pressure chamber, and through and out of said U-shaped outlet housing without disturbing the pressure balance within said housings.
 3. Apparatus for continuous thermal treatment of products contained in said apparatus in sealed containers, comprising in combination an endless conveyor for transport of containers, a vessel having at least one inlet hydrostatic column, means defining at least one constant pressure treatment chamber communicating with said first column, and at least one outlet hydrostatic column communicating with said chamber, means for advancing said conveyor through said vessel along a path of travel successively passing through the inlet column, the treatment chamber and the outlet column, said treatment chamber including a major portion of substantially horizontal elongate form, a liquid filling said major portion of the treatment chamber, means for maintaining said liquid at a predetermined treatment temperature, means for introducing and for maintaining in said chamber a gaseous fluid having an overpressure, the value of which is greater than the vapor pressure of said liquid at said temperature, said overpressure being balanced by said columns, and idlers in said major portion of said treatment chamber for said conveyor arranged to cause the conveyor to travel in at least one substantially horizontal run through the liquid in said major portion of the chamber.
 4. Apparatus for continuous thermal treatment of products contained in said apparatus in sealed containers, comprising in combination an endless conveyor for transport of containers, a vessel having at least one inlet hydrostatic column, means defining at least one constant pressure treatment chamber communicating with said first column, and at least one outlet hydrostatic column communicating with said chamber, means for advancing said conveyor through said vessel along a path of travel successively passing through the inlet column, the treatment chamber and the outlet column, a liquid with its vapor in said chamber, means for maintaining said liquid at a predetermined treatment temperature, means for introducing and for maintaining in said chamber a gaseous fluid having an overpressure, the value of which is greater than the vapor pressure of said liquid at said temperature, said overpressure being balanced by said columns, and means in said treatment chamber for dividing the liquid and impinging the same under pressure at said treatment temperature against the containers along the length of the conveyor in said treatment chamber.
 5. Apparatus as claimed in claim 4 wherein said means for dividing and impinging the liquid against the containers is located on both sides of the conveyor.
 6. Apparatus as claimed in claim 4 wherein said means for dividing and impinging the liquid on both sides of the conveyor comprises a pump connected to a reservoir of said liquid, maintained in the chamber at said treatment temperature and overpressure, for circulating the latter liquid and effecting division and direct impingement thereof against the containers.
 7. Apparatus as claimed in claim 4 comprising receptacles on said conveyor for receiving the containers, said receptacles being perforated over their entire surface to permit successive vertical streaming along their length.
 8. A method of continuous thermal treatment of products contained in sealed containers, said method comprising the steps of conveying said containers along a path of travel comprising in succession at least one inlet hydrostatic pressure column, at least on treatment chamber under constant pressure and at least one outlet hydrostatic pressure column, forming said treatment chamber of substantially horizontal elongate shape, filling said chamber with a liquid, maintaiNing the liquid at a predetermined treatment temperature, subjecting said liquid in said chamber to an overpressure with a gaseous fluid, the pressure of which is constantly maintained to a value greater that the saturated vapor pressure of said liquid at said treatment temperature, said overpressure being balanced by said hydrostatic columns, and passing the conveyor along at least one immersed horizontal run in the liquid in said chamber.
 9. A method of continuous thermal treatment of products contained in sealed containers, said method comprising the steps of conveying said containers along a path of travel comprising in succession at least one inlet hydrostatic pressure column, at least one treatment chamber under constant pressure and at least one outlet hydrostatic pressure column, subjecting said containers traveling in said chamber to the action of a liquid contained in said chamber and maintained at a predetermined treatment temperature, subjecting said liquid and its vapor in said chamber to an overpressure with a gaseous fluid, the pressure of which is constantly maintained to a value greater than the saturated vapor pressure of said liquid at said treatment temperature, said overpressure being balanced by said hydrostatic columns, said containers being subjected to the action of said liquid by dividing the liquid and impinging the same against the containers at said treatment temperature and pressure along the length of travel in the treatment chambers.
 10. A method as claimed in claim 9 wherein liquid is maintained in the treatment chamber in a reservoir at the bottom thereof, and the liquid which impinges on the containers is recirculated from said reservoir.
 11. Apparatus for continuous thermal treatment of products contained in sealed containers, comprising an endless conveyor for transport of containers, a vessel having at least one inlet hydrostatic column, at least one vertical treatment chamber communicating with said first column, and at least one outlet hydrostatic column communicating with said chamber, means for advancing said conveyor through said vessel along a path of travel successively passing through the inlet column, the treatment chamber and the outlet column, a treatment liquid at the bottom of said vertical chamber, means for maintaining said liquid at a predetermined treatment temperature, means for introducing a gaseous fluid into said chamber and for maintaining at a constant level the said liquid and for maintaining inside the treatment chamber a constant overpressure the value of which is greater than the vapor pressure of said liquid at said treatment temperature, said overpressure being balanced by said hydrostatic columns, and a circulating pump for pumping the treatment liquid at the bottom of the treatment chamber and spreading it in divided form at the top of the said treatment chamber. 